The present invention provides a means to aid golfers in visualizing the effect of gravity on a putt or other golf stroke that causes a ball to roll across a sloped surface.
Greens on golf courses are generally sloped to provide drainage for the grass and challenge for the golfer. In order to avoid standing water the green usually has no local low spots or concavities. Thus, a green is usually either planar or crowned (i.e. higher in the middle than at the edges). Moreover, the front of the green (i.e. that portion closer to the tee) is generally lower than the back of the green so that the golfer can "hold" the green on approach shots.
When a green slopes, the path along which the ball must be putted in order for it to reach the cup is usually not the same as the straight line of sight from the ball to the cup. Unless the line of sight from the ball to the cup is directly uphill or directly downhill, gravity will cause the ball to "break" away from that line. In order to succeed at putting, the golfer must predict the break, which is a function of both the slope and the "speed" of the green. "Speed", a complex function of the height of the grass, dampness of the green, etc., is estimated subjectively by the golfer, based on his experiences with similar greens. Slope, on the other hand, is far more tractable to measurement and the prior art is replete with devices that allow a golfer to "read" the slope of the green. Notable among these are U.S. Pat. Nos.
4,984,791 to Labell, who teaches the use of a pair of bubble levels to allow the golfer to measure the slope of the green in two perpendicular directions, PA1 4,821,114 to Catalano, who uses a plumb bob inside a putter to measure the slope and to indicate a predicted path for the ball, PA1 3,679,206, to Shambaugh, who teaches a multi-part device that indicates a line of swing for a selected one of a variety of clubs if the golfer is to hit a ball from a "cross-hill lie", PA1 3,535,792, to Douglas, who employs a pendulum to determine a vertical direction and a manually pivoted scale set to visually match the surface of the green, thereby displaying the angle of the slope, and PA1 3,293,755, to Cronwell, who employs a pendulum that is constrained to move in a single plane and that is part of a rotatable body that can, if once read and twice rotated, indicate a stroking direction for a putt.
Although the aforementioned instruments may be useful as training aids, the "Rules of Golf" (published by the United States Golf Association as Publication 14-3) forbids the use of devices or equipment that measure or gauge distance or conditions.
With or without the aid of a measuring device, a successful putt requires that the golfer estimate the net slope of the green, preferably by first reading the slope in two perpendicular directions and then assessing the effect of gravity on his putt in order to select an initial stroking direction. Many golfers take pains to observe the slopes, but still misread the green by erring when they mentally combine the effects of the two slopes. When this happens, the golfer may, for example, stroke his putt along an initial path that is to the left of the cup, and watch in frustration as the ball breaks even further to the left.